Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$149.75	10.865%	$166.0203	$166.02	$166.00	$166.00
Purchase #2	$127.65	13.737%	$145.1853	$145.19	$145.20	$145.20
Purchase #3	$216.51	6.529%	$230.6459	$230.65	$230.65	$230.60
Purchase #4	$27.61	11.349%	$30.7435	$30.74	$30.75	$30.70
Purchase #5	$86.40	4.483%	$90.2733	$90.27	$90.25	$90.30
Purchase #6	$159.99	8.671%	$173.8627	$173.86	$173.85	$173.90
Purchase #7	$210.86	6.620%	$224.8189	$224.82	$224.80	$224.80
7 purchase totals =	$978.77		$1,061.5499	$1,061.55	$1,061.50	$1,061.50